Linear electric motors are well known devices. In such a motor, there is provided a stationary shell, in which is mounted a linearly movable member, such as a shaft or a piston. One of the shell and movable member has a magnet or a set of magnets mounted to it, and the other has a coil that receives operating electric current. Supply of operating electric current to the coil produces a magnetic field that interacts with the magnet to produce linear movement of the movable member.
When applied to hermetic compressors of refrigeration, the linear electric motor moves a piston inside a cylinder to compress the refrigerant gas. At least one type of these hermetic compressors of refrigeration uses a linear motor, in which the coil that receives the operating electric current is fixedly mounted to the shell or block of the compressor in which the cylinder is formed, and the magnet or magnets are mounted to the movable member that carries the piston. A resonant assembly driven by the linear motor has the function to develop a linear reciprocating movement, resulting in the movement of the piston inside the cylinder exerting a compression action on the gas received through a suction valve of the compressor, until the point is reached in which the gas is discharged to the high pressure side of the compressor.
In these hermetic compressors of refrigeration, the magnet or magnets is/are mounted to a support carried by the piston. The construction of the support presents several technical difficulties, one of these resulting from the fact that the material of the support is subjected to the magnetic field produced by the coil. Since the support is movable and exposed to the magnetic field, if it is made of a metallic material, for example stainless steel, the material of the support generates Foucault currents, causing energy losses.
The problem of losses due to Foucault currents is known and solutions have been proposed, such as those disclosed in U.S. Pat. Nos. 5,642,088, 5,751,075, and 6,097,125. In U.S. Pat. No. 6,097,125, a “cylindrical cup” made of a non-magnetic material is provided to reduce the effect of losses due to Foucault currents, the cup having grooves located between its internal and external walls in which the magnets are mounted. Such structure is constructively complex and presents high costs with material for producing the cup shaped support.
By reason of the above, there is a need for providing a support for a linear electric motor to attach the magnets of said motor, having low cost and a construction that minimizes energy losses caused by Foucault currents. It is also desired the provision of such a magnet support structure for use in a refrigeration compressor, in which the piston is linearly reciprocated by the action of a linear electric motor.